The social transactions of popular, rejected, neglected, and average first- and third-grade boys were examined during their initial encounters with peers. 23 groups of 5 or 6 boys each were observed for 45-min free-play sessions conducted on 5 consecutive days, with sociometric interviews following each session. Social preference in the play groups correlated significantly with classroom social preference after the third and subsequent play sessions for the third graders, and after the fourth and subsequent sessions for the first graders. The observational coding system distinguished 4 types of aggressive behavior that were hypothesized to relate to peer status in different ways. The first, rough play, was not related to peer status. However, rejected boys at both ages displayed significantly higher rates of angry reactive aggression and instrumental aggression than average boys. The relation between bullying and peer status varied with the age of the child. Popular first graders engaged in more bullying than average first graders, but popular third graders did not differ from average in bullying. Other questions concerned the temporal relation between play group behaviors and social preference scores within the group. Socially interactive behaviors anteceded high preference by peers, and low preference in turn led to social isolation in subsequent sessions.